ESC 1000 CHAPTER 5 QUIZ 9

In elastic rebound theory, what must occur to produce an earthquake?

Enough stress must build up over time on a fault to overcome friction.

Faults are "locked" because ________.

high confining pressure increases friction on the fault

Seismic gaps are places where scientists think that ________.

faults are storing elastic strain

The figure below shows the intensity of an Earthquake in northern California that affected much of the same areas that were damaged by the 1906 earthquake in a very similar manner. Based on this information, ________.

in general, the current building codes are adequate, but people should be aware of the hazards in this area

Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with a Richter magnitude of 5.5?

30 times

The earth's major layers formed because ________.

the earth was heated after its formation resulting in melting and redistribution of major chemical compositions

The epicenter of an earthquake is on the surface of the Earth directly above the focus.

true

Which of the following is determined by measuring the amplitude of waves recorded from an earthquake?

magnitude

Structural damage from seismic vibrations would be worse ________.

where older buildings were built on a thick layer of sediment

Megathrusts between subducting oceanic crust and an overriding plate are a potential source of tsunamis because ________.

the earthquakes on these faults are underwater and could displace large amounts of water from the oceans

The position on Earth's surface directly above the earthquake source is called the ________.

epicenter

What is the probability that a large earthquake (M > 6.7) will occur in the San Francisco area between 2003 and 2032?

62%

The earliest seismographs were designed by the Chinese nearly 2000 years ago to measure ________.

the direction to the earthquake focus

Major earthquakes are often followed by somewhat smaller events known as ________.

aftershocks

Oceanic crust is composed primarily of ________.

basalt

One measurement that is widely used to determine how far the focus of an earthquake is from the seismograph where it is recorded is ________.

the difference in travel time between the P and the S wave

In the open ocean, Tsunamis travel at about the same speed as a commercial airliner.

true

Turnagain Heights, was badly damaged by a landslide during the 1964 Alaskan earthquake.

true

Earthquakes result from the sudden release of elastic energy previously stored in rocks surrounding a zone of fault movement.

true

The Richter earthquake magnitude scale is based on the energy released by the earthquake.

true

During the 1906 San Francisco earthquake, the movement of the Pacific Plate was approximately ________.

10 meters

The velocity of seismic waves generally increases with depth in the earth.

True

________ is the maximum possible damage designation on the Mercalli scale.

XII

We are fortunate in the United States that large tsunamis do not affect most of our coastal regions except in Hawaii.

false

The 2011 earthquake and tsunami in Japan killed approximately 21,000 people while the 2010 earthquake in Haiti killed approximately 316,000 people because ________.

the construction methods in Haiti were not as good as those used in Japan

A few days before a major earthquake in China, one village in the area reported the streets were filled with migrating toads that might have indicated the impending event.

true

The next large earthquake on the San Andreas Fault zone in California is considered likely to be ________.

in Southern California because it has been nearly 300 years since the last major earthquake in that area

P waves ________.

are faster than S waves and surface waves

During the Alaskan earthquake of 1964, the buildings that survived the best were made of wood.

True

Earthquakes along the San Andreas fault zone, for example, are repetitive—they reoccur in roughly the same regions over and over again—separated by decades or centuries because ________.

stress continues to build up all the time and when it is great enough to overcome friction there will be an earthquake and then the process will start over again

If you are on a beach, you might recognize that a tsunami is approaching because ________.

the water will withdraw from the beach farther than usual

Large megathrust earthquakes in the mountainous regions flanking the Mediterranean sea are generally due to ________.

the collision of the African Plate with Eurasia

Earthquakes with a very deep focus are usually located along ________.

a convergent boundary such as the Peru-Chile trench

Large earthquakes almost always produce new faults because the old faults tend to "heal" in the long time that separates most large earthquakes.

false

The ocean ridge systems that make up the major divergent plate boundaries are a source of frequent large earthquakes and tsunamis.

false

Modern seismographs rely on ________ to record the ground motion from an earthquake.

inertia

Felt earthquakes usually last for ________.

10 to 60 seconds

On a typical seismogram, ________ will show the highest amplitudes.

surface waves

When an earthquake occurs, energy radiates in all directions from its source. The source is also referred to as the ________.

focus

Which one of the following statements is correct?

P and S waves travel through solids and P waves travel through liquids.

Overall, this type of seismic wave is the most destructive.

surface waves